Sediment Transport in an Urbanizing Karst Aquifer-Watershed

0001197 Bennett地下水通过岩溶含水层的湍流有效地将沉积物和胶体输送到地下，并可能为有机污染物的快速输送提供途径。 相比之下，岩溶含水层中的沉积物储存可能会长期隔离污染物，同时改变含水层的流动特性。 岩溶含水层中沉积物的可利用性和迁移反过来又受到土地利用变化以及相关的径流和河流流量变化的深刻影响。 虽然对地表水泥沙输运的水动力学进行了广泛的研究，但对岩溶水动力学知之甚少，对地表和地下区域之间的联系知之甚少，对岩溶含水层泥沙输运的动力学几乎一无所知。 拟议的研究将调查运输的沉积物在城市化的巴顿溪部分的爱德华兹含水层分水岭得克萨斯州中部。 沉积物特性，沉积物输运和沉积物化学将在巴顿溪在西南奥斯汀的主要补给区，进入含水层，并在流域的唯一排放点在巴顿和冷泉。 该项目的目标是：1）确定补给点河流中沉积物的化学性质，并将其与排出的沉积物进行比较; 2）使用天然和引入的示踪剂，量化沉积物通过这一含水层段的迁移情况;和3）量化不同流态下城市化和农业流域的沉积物收支。我们将在底部描述巴顿溪径流中的沉积物特征在巴顿和冷泉排放点，以及在补给点和排放点之间使用几口监测威尔斯井直接在含水层中进行监测。 将通过比较进入含水层的沉积物“补给”与泉水处的沉积物排出量，建立沉积物质量平衡。 将在基流和暴雨流条件下采集样本，以检查沉积物负荷、粒度分布和矿物学随流量的变化。 与奥斯汀市合作，使用荧光染料追踪水流，以及天然和引进的沉积物示踪剂，将用于描述岩溶含水层中的沉积物运移特征。 一种新的沉积物示踪剂使用DNA标记的粘土将被用来量化运输时间的补给功能和损失的沉积物储存在含水层。 通过分析表层沉积物有机碳来确定悬浮沉积物污染物迁移的可能性，通过分析选定沉积物样品的总石油烃来确定污染物负载的特征。该项目将提供对进入和通过岩溶含水层的沉积物迁移过程、沉积物和沉积物结合的污染物的流动性、以及城乡流域移动的泥沙来源。

0001197BennettThe turbulent flow of groundwater through karst-aquifers effectively transports sediment and colloids through the subsurface and may provide a pathway for the rapid transport of organic contaminants. Sediment storage in karst aquifers, in contrast, may sequester contaminants for long time periods while altering the flow properties of the aquifer. The availability and transport of sediment in a karst aquifer are in turn profoundly influenced by changes in land-use and the associated changes in runoff and stream discharge. While there has been extensive research into the hydrodynamics of sediment transport in surface water, little is known about karst hydrodynamics, less about the connection between the surface and subsurface domains, and almost nothing about the dynamics of sediment transport in karst aquifers. The proposed study will investigate the transport of sediment in the urbanizing Barton Creek segment of the Edwards aquifer watershed of central Texas. Sediment characteristics, sediment transport, and sediment chemistry will be examined in Barton Creek across the primary recharge area in SW Austin, into the aquifer, and out at the watershed's only discharge points at Barton and Cold Springs. The goals of this project are to 1) Characterize the sediment chemistry in the stream at the recharge point and compare that to the discharged sediment; 2) quantify the transport of sediment through this section of the aquifer using natural and introduced tracers; and 3) quantify the sediment budget in urbanizing and agricultural watersheds under different flow regimes.We will characterize the sediment in the Barton Creek runoff at base and stormflow stages, at the Barton and Cold Springs discharge points, and directly in the aquifer using several monitoring wells between the recharge and discharge points. A sediment mass-balance will be developed by comparing sediment 'recharge' into the aquifer to sediment discharge at the springs. Samples will be collected during baseflow and stormflow conditions to examine sediment loading, size distribution, and mineralogy as a function of discharge. Tracing of water flow using fluorescent dyes in cooperation with the City of Austin, and both natural and introduced sediment tracers, will be used to characterize sediment transport in the karst aquifer. A novel sediment tracer using DNA-labeled clay will be used to quantify transport time from the recharge feature and the loss of sediment to storage in the aquifer. The potential for contaminant transport by suspended sediment will be characterized by analyzing surface area sediment organic carbon, and contaminant loading will be characterized by analysis of total petroleum hydrocarbons on selected sediment samples.This project will provide fundamental insight into sediment transport processes into and through karst aquifers, the mobility of sediment and sediment-bound contaminants, and the sources of mobile sediment in urban and rural watersheds.